Are you sure the prescription is fine?
I bought some prescription sunglasses fro D&A and never wore them because they gave me a headache.. when I finally gave up, and went to another opticians to have my eyes re-tested, I found that D&A had given me the wrong prescription.. in fact, the optician didn't actually test my eyes at all, he just said "same as before!" and like a mug, I didn't question it.
Hence, I'm never going to set foot in the charlatans again.
I've just bought some fab Chanel frames, cost £185. Not going to get my eyes tested until I've been signed off from the eye hospital later this year.. but generally pay about £200 per lens.